Possible Endometriosis?

For about 5 months I experience excruciating pain from gas and constipation while on my period. I do not experience pain any other time or bowel issues, just when I have my period. I had an x-ray done that showed I was constipated. However, the doctor said to see my OBGYN to see if she can check for endo because I should not be in that much pain from constipation. I am scared to get checked because infertility is one of my biggest fears. Did anyone else only have this symptom and then diagnosed with endometriosis?